1. Field of the Invention
The present invention relates to a seat belt retractor for use in an automotive vehicle. In particular, the present invention relates to a seat belt retractor having a comfort mechanism for preventing tension exerted by the seat belt webbing from acting against a vehicle occupant during nonemergency situations.
2. Description of the Prior Art
A known seat belt retractor of the vehicle sensitive and web sensitive type is disclosed in U.S. Pat. No. 4,467,480. The retractor has a spool or spindle to which seat belt webbing is connected. The spindle is supported for rotation in the belt withdrawal and belt retraction directions. A first ratchet wheel is connected to and rotates with the spindle. A locking pawl is supported for pivotal movement into engagement with the first ratchet wheel for blocking rotation of the spindle in the belt withdrawal direction. The seat belt retractor is web sensitive. Thus, the spindle is blocked from rotating in the belt withdrawal direction in response to the seat belt webbing being withdrawn at a rate above a predetermined rate. An inertia member lags behind the rotation of the spindle when the seat belt webbing is withdrawn above the predetermined rate. The spindle, thus, rotates relative to the inertia member and the locking pawl is moved into engagement with the first ratchet wheel.
The seat belt retractor is also vehicle sensitive. Specifically, the inertia member has a plurality of teeth extending therefrom. A mass moves in response to acceleration or deceleration of the vehicle above a predetermined rate to pivot a lever toward the inertia member. When the spindle is rotated in the belt withdrawal direction, a tooth on the inertia member engages the lever to block rotation of the inertia member in the belt withdrawal direction. Thus, upon rotation of the spindle in the belt withdrawal direction, rotation of the spindle relative to the inertia member occurs and the locking pawl is moved into engagement with the first ratchet wheel.
Such a seat belt retractor may also include a comfort mechanism or a tension eliminator to reduce the force of a retraction or return spring acting through the seat belt webbing against a vehicle occupant. The comfort mechanism includes a second ratchet wheel connected with the spool for joint rotation. A comfort member is brought into engagement with a tooth of the second ratchet wheel to actuate the comfort mechanism and prevent rotation of the spindle in the belt retraction direction.
The retractor may encounter a condition termed a "double lock" in which the spindle is blocked from rotating in both the belt retraction and the belt withdrawal directions. The "double lock" can occur when the comfort mechanism is actuated by the comfort member engaging a tooth on the second ratchet wheel and the lever simultaneously engages a tooth on the inertia member.